1) write {{ color_alpha('rgb(0,0,0)', 50) }}
result
An exception has been thrown during the rendering of a template ("Undefined offset: 3").
2) write {{ color_alpha('rgba(0,0,0,0.1)', 50) }} or {{ color_red('rgba(0,0,0,0.1)', 50) }}
result
An exception has been thrown during the rendering of a template ("Undefined offset: 4").

I looked through the code and think I might have found the issue that caused it. Update to 1.0.2 and please let me know if it works as it should now since I don't have any way of testing the code currently, I'm not an active user of octobercms any longer

its work! thank you!